Plant-Based Diets and Bariatric Surgery



Is it fine to cut the meat (and more) after bariatric surgery?

This was the question we posed in the last free Bariatric Cookery Newsletter (click to see here). Is it a wise move for someone who has had WLS? There are now so many varied dietary regimes and some might well be better or more challenging for the  post-op patient.

So we asked our guest dietitian Nichola if she could outline the various diets; tell us the issues that might arise with nutrition on these regimes; and does she recommend them or have some cautionary advice. 

I thought her feature was most interesting and illuminating – I learnt a great deal from it and felt I could better navigate my way through the dietary options available to me. As a result I also checked out some of the meatless and vegan protein sources available (and you can see them at a glance in the charts at the end of this blog).

Unless you are a newsletter subscriber (it’s free and you can subscribe by clicking here) you may not have seen this feature so we are reproducing here so that you can read and re-read if necessary.


Plant-Based Diets & Bariatric Surgery


By Nichola Ludlam-Raine, Registered Dietitian at Ramsay Health Care



What is a Plant-Based Diet?


Plant-based diets are growing in popularity, and depending on the type of plant-based diet, the following foods may or may not be eaten; eggs, milk, cheese, yoghurt, honey, fish, poultry and meat. Individuals may choose to follow a plant-based diet for a number of reasons including animal welfare, personal health reasons and environmental concerns.


Regarding health, there are a number of different eating patterns associated with good health and longevity, and whilst some include meat, others do not:


  • Mediterranean Diets – limit red meat, but include poultry and fish.
  • Traditional high carbohydrate Asian-style Diets – include meat in small amounts, as well as fish.
  • Vegetarian Diets – exclude meat, although pescatarians eat fish.
  • Vegan Diets – exclude meat, egg, dairy and honey.


They key is to look at what these diets have in common i.e. they are high in fruits, vegetables, whole-grains and unsaturated fats, and are low in foods that are high in sugar and fat and low in nutrients.



Are Plant-Based Diets Healthy?


A well-planned plant-based diet can be both nutritious and healthy, and meat-free diets have indeed been associated with lower risks of heart disease, high blood pressure, type 2 diabetes, obesity and various cancers. It’s worth noting though that most of the research is only observational and many vegetarians/vegans may be more health conscious; thus being more likely to exercise and less likely to smoke.


A new style of diet has however recently emerged; instead of following a strict vegetarian or vegan diet, many people are now choosing to follow a ‘flexitarian plan’. Eating in accordance to a ‘flexitarian plan’ involves eating mainly/more plant-based foods i.e. lentils, beans, pulses, fruit, vegetables and whole-grains, but still includes meat and/or fish occasionally.


Eating more plant-based foods is always a good thing as these foods tend to be higher in fibre (more beans, pulses, fruits, vegetables and whole-grains) as well as healthy unsaturated fats from nuts, seeds, olive oil, rapeseed oil and avocados.


If you’re vegan though you need to have a well planned and varied diet to make sure you’re getting enough protein as well as certain nutrients including calcium, iodine, iron and B12; for which many vegans actually take a supplement.


Plant-Based Diets & Bariatric Surgery


Following gastric bypass and gastric sleeve surgery your body’s ability to absorb vitamin B12 is severely impaired due to loss of the intrinsic factor; this is why you need a 1mg vitamin B12 injection every 3 months, starting 3 months after surgery, for the rest of your life.


Protein is also essential following weight loss surgery and during the initial weeks you may be reliant upon milk to meet your needs. Soya milk contains a similar amount of protein in comparison to cow’s milk, however nut milks contain hardly any. If you rely on nut milks then you may need to consider adding a plant-based protein powder: look for one that provides a mixture of different sources of protein to ensure that you’re getting a range of different amino acids (the breakdown of protein) such as hemp, pea and rice protein.


Meat and fish are excellent sources of protein, as well as other nutrients, and although following weight loss surgery you may struggle to eat certain types of meat or indeed the quantity of meat that you ate prior e.g. steak or fried chicken, you should be able to eat meats such as minced beef or casseroled chicken.


Nutrients to be Aware of if Eating a Plant-Based Diet


  • Protein for muscle growth and repair, in addition to muscle preservation when losing weight = If you avoid meat and fish aim to eat a variety of different proteins to ensure that you’re getting all of the essential amino acids (the building blocks of protein) that the body cannot make e.g. tofu, lentils, chickpeas, beans, nuts, seeds, soya and whole grains.
  • Omega 3 fatty acids for heart health = If you don’t eat oily fish make sure to include foods such as flaxseed oil, tofu and walnuts/pumpkin seeds regularly and consider taking an Algal supplement which contains the most beneficial type of omega 3 fatty acid DHA; the body doesn’t convert ALA (the plant based type omega 3) to DHA and EPA very well.
  • Calcium for bone and teeth health = If you don’t drink milk or eat dairy, make sure to choose fortified milk alternatives (this means that calcium is added in), figs, sesame seeds, calcium-set tofu and almonds. You should also take your daily calcium supplement as directed by your dietitian or doctor if you have had a gastric bypass or sleeve.
  • Iodine for thyroid function = Iodine is mainly found in dairy and white fish. If you avoid these foods you could consider having a portion of seaweed a week, however your multivitamin should contain this.
  • Iron transports oxygen around the body = Vegan sources of iron include lentils, soybeans, tofu, dried fruit, dark green vegetables, wholemeal bread and fortified breakfast cereals (none vegan sources include meat, eggs and fish). Have these foods with a source of vitamin C (such as fruit and vegetables) to enhance absorption and keep tea and coffee to 30 minutes either side as they can inhibit iron absorption. You should also take your daily iron supplement as directed by your dietitian or doctor if you have had a gastric bypass or sleeve.
  • Vitamin B12 supports energy levels = In addition to your vitamin B12 injections you could look at consuming fortified milk alternatives (where B12 is added as an ingredient), nutritional yeast and marmite. Your multivitamin should also contain this.
  • Selenium for a healthy immune system = Try having 2-3 Brazil nuts a day to ensure you’re getting this essential mineral. Your daily multivitamin should also contain this.
  • Vitamin D helps you to absorb calcium = Vitamin D is found in oily fish and eggs as well as vegan sources including fortified breakfast cereals and milk alternatives. You should also take your daily vitamin D supplement (often included in the calcium supplement) as directed by your dietitian or doctor if you have had a gastric bypass or sleeve.




Eating more plant-based foods is not only good for the environment but it can have a positive effect on your health too. There is however no need to cut out foods such as meat, poultry and dairy altogether, especially if you enjoy them as they are good sources of protein as well as vitamins and minerals.


As a dietitian I wouldn’t recommend taking up a vegetarian or vegan diet following weight loss surgery, but rather focus on eating better quality meats in smaller quantities i.e. choosing leaner cuts of meat as opposed to processed meats such as bacon, burgers and sausages.


And remember, foods including deep fried chips and sugar are vegan too; so it isn’t a guaranteed healthy diet!



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